Beam-guiding and/or frequency-converting optical system and method for producing the same

ABSTRACT

The present invention relates to a beam-guiding and/or frequency-converting optical system as well as to a method of manufacturing same, wherein a beam-emitting optoelectronic component ( 1 ), which comprises at least one beam-emerging surface ( 2 ) for the emergence of a beam, is provided and connected to a surface ( 5 ) of a base ( 4 ) in such a manner that the emerging beam extends approximately in parallel with the surface ( 5 ) of said base ( 4 ). Once the optoelectronic component ( 1 ) has been connected to said base ( 4 ), a wave-guiding stratified system ( 4 ) is deposited and structured and/or locally modified on the surface ( 5 ) of said base ( 4 ) for guidance and/or frequency conversion of the beam in such a way that a gap-free contact is created between said beam exit surface ( 2 ) and said stratified ( 6 ) and a pre-determinable beam guidance is achieved.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing abeam-guiding and/or frequency-converting optical system wherein abeam-emitting optoelectronic component is provided, which comprises atleast one beam exit surface for the emergence of a beam, and connectedto the surface of a base in such a way that the emerging beam extendsapproximately in parallel with the surface of the base. The inventionrelates moreover to a beam-guiding and/or frequency converting opticalsystem that can be produced by this method.

Guiding and converting electromagnetic radiation from optoelectroniccomponents such as semiconductor diode lasers plays an important role inmany fields in technology where optoelectronic components are employed.In these methods, the radiation emerging from the optoelectroniccomponent is, as a rule, guided or shaped by further optical componentsin order to achieve the beam characteristics required for the respectiveapplication. In many cases, conversion of the frequency of the radiationemerging from the optoelectronic component into a higher or lowerfrequency is equally required.

PRIOR ART

As a rule, further discrete optical components such as lenses, opticalwaveguide fibres or frequency-doubling crystals are provided in adiscrete optical structure for guiding and converting theelectromagnetic radiation from optoelectronic components. In thesesystems, the optoelectronic component and likewise the beam-guiding orfrequency-converting components are mounted and adjusted on a base. Theprovision of an optical system in which the radiation of theoptoelectronic component is shaped and guided by means of lenses and/ormirrors and coupled into optical guiding fibres requires a great numberof adjusting steps. For example, the optoelectronic component mustinitially be aligned and mounted on the base. Then the lenses and/ormirrors are adjusted in succession, relative to the optoelectroniccomponent, and fixed on the base. Subsequently, the optical waveguidefibre is adjusted and mounted on the base. The precise adjustment andmounting of the individual discrete components is a tedious andexpensive operation susceptible to faults. Moreover, undesirable opticallosses occur between the separate components, which are caused, forinstance, by reflection, scattering and diffraction of the light.

The German Patent DE 695 10 238 T2 discloses a microchip laser thatincludes one or several integrated beam-shaping or frequency-convertingelements, respectively. Microchip lasers consist of combined polisheddielectric materials such as laser crystals or frequency-doublingcrystals that are pumped by high-power diode lasers. For example, theGerman Patent DE 695 10 238 T2 discloses a microchip laser that issubstantially composed of a layer of amplifying material, a layer of acarrier material, e.g. quartz crystal, and a layer consisting of afrequency-doubling crystal. The layer of the carrier material serves tomount the laser on a base or substrate on which the diode pumping laseris mounted as well. When the carrier layer is configured on one end ofthe microchip laser it may assume, at the same time, the function of abeam-shaping lens if it is appropriately shaped. For the production ofsuch a microchip laser it is necessary that the contact surfaces of thecrystals used as amplifying layer and as frequency-doubling layer and ofthe carriers are highly polished and plane in order to ensure that thematerials will be joined by Van-der-Waals forces when they arecompressed. The production of such a microchip laser is thereforeexpensive. With comparable output power, microchip lasers achieve adistinctly improved beam quality, compared against laser diodes, in thevisible spectral range. The insufficient stability of the beam axis(beam point stability) of these lasers is, however, a disadvantage thatprecludes many potential applications, e.g. in metrology such as lasertriangulation and in printing technology.

Another known beam-guiding and/or frequency-converting optical systemmakes use of the technique of bonded waveguides. Bonded planarwaveguides and waveguide lasers are composed of thin polishedmono-crystals and pumped by means of high-power diode lasers via abeam-shaping stage consisting of two cylinder lenses. One example of theapplication of this technology of bonded waveguides is known, forinstance, from C. Li et al. “Longitudinally Diode-Pumped High-PowerWaveguide Lasers” in: Proceedings 10^(th) European Conference onIntegrated Optics, Paderborn, Germany, pages 83 to 86, 2001. Thewaveguide lasers used in this technique consist of a combination oflayers of sapphire, YAG, Nd:YAG, YAG and sapphire, with the individuallayers presenting a thickness as small as roughly 5 to 20 μm, at an areain the range of square centimetres. With such waveguide lasers powerlevels above 1 Watt can be achieved at a wave-length of 1064 nm almostwith restriction of diffraction. This concept involves, however, thedisadvantage of the extremely expensive thin design of the crystalplatelets and the expensive and tedious adjustment and mounting workresulting in a very high expenditure in terms of manufacture.

Starting out from such prior art, the present invention is based on theproblem of providing a method of producing a beam-guiding and/orfrequency-converting optical system that requires only a slightexpenditure in terms of manufacture and furnishes a highly efficientoptical system. Moreover, a beam-guiding and/or frequency-converting,highly efficient optical system is envisaged that can be produced bythis method.

DESCRIPTION OF THE INVENTION

This problem is solved by the method and by the system according to thePatent Claims 1 or 16, respectively.

Expedient embodiments of the method as well as of the system are thesubject matters of the dependent claims or can be derived from thefollowing description and the embodiments.

In the present method of manufacturing a beam-guiding and/orfrequency-converting optical system, a beam-emitting optoelectroniccomponent is provided that is provided with at least one beam exitsurface for the emergence of a beam and is connected to a surface of abase in such a way that the emerging beam extends approximately inparallel with the surface of the base. Once the optoelectronic componenthas been connected to the base, for instance a carrier substrate, anoptical wave-guiding stratified system composed of several layers isdeposited and structured and/or locally modified on the surface of thebase for guidance and/or frequency conversion of the beam in such amanner that a gap-free contact is created between the beam exit surfaceof the optoelectronic component and the stratified system whilst a beamguidance is achieved that can be predetermined. With the present methodhence a novel system is provided that consists of optical waveguidesahead of optoelectronic beam sources for guiding and/or converting thelight of the beam source, wherein the waveguides are manufactured indirect contact with the beam source by depositing and structuring alayer and/or by modifying the stratified system on a common base. Theindividual layers of the stratified system are preferably made ofglass-like, ceramic or polymer materials, which must, of course, permitthe transmission of the light for beam guidance or frequency conversion,respectively. In distinction from the technique of manufacturing microchip lasers, which has been described by way of introduction, thepresent method involves a hybrid rather than a monolithic integration ofoptical and optoelectronic components.

One essential advantage of the present method and the appertainingsystem resides in an improvement of the efficiency of the optical systembecause coupling losses between the optoelectronic component and thewave-guiding stratified system are avoided by the direct contact, whichlosses are unavoidable in the case of a discrete optical structure.Moreover, the present method results in an improvement of the efficiencyin the manufacture of such optical systems because the hybridintegration of the wave-guiding structures with the optoelectroniccomponent on a common base saves expensive and complex adjusting andmounting operations. The present method presents also advantages overthe techniques of manufacturing micro chip lasers or bonded waveguidesbecause the complex polishing and adjustment of the beam-guiding orfrequency-converting wave-guiding structure is not required.

One or several ones among the layers of the wave-guiding stratifiedsystem are so structured in the present method that the resultingwave-guiding structure permits the desired guidance or shaping of thebeam emerging from the optoelectronic component. The suitable selectionof the materials and dimensions of this stratified structure are commonto those skilled in the art. The wave-guiding stratified systempreferably consists of at least three superimposed layers whereof themiddle layer has a refractive index higher than the index of the twoneighbouring layers. Individual layers of the wave-guiding stratifiedsystem or of the entire stratified system, respectively, can bestructured already by depositing in a structured manner, using one orseveral masks. Moreover, the layers can also be structured by removingprocesses in an appropriate manner after the layers have been deposited.A local modification of the characteristics of the deposited layers, forinstance under the influence of laser radiation for a local variation ofthe refractive index, is possible, of course, too.

For both depositing the layers and for structuring or modificationprocesses are employed that do not impair the function of theoptoelectronic device or the connection between the optoelectronicdevice and the base. High temperatures and strong electric fields inparticular must be avoided in this operation. For this reason, methodsare preferably applied which operate on hyperthermic particles such ashigh-speed ions and on pulsed laser radiation, for instance methods oflaser deposition, ion beam deposition, of cathodic sputtering, ofreactive ion etching or of removal or variation of the refractive indexby means of pulsed laser radiation. For the manufacture of the gap-freecontact between the wave-guiding stratified system and the at least onebeam exit surface of the optoelectronic component one should select asubstantially directional deposition at an angle that is approximatelyparallel to the beam exit surface of the optoelectronic component.

For a frequency-converting function, preferably a wave-guidingstratified system is deposited, wherein at least one layer is formed ofa laser-active material—which means a fluorescent material, forinstance—that can be excited by the frequency of the beam emerging fromthe optoelectronic component (first frequency) and is emissive inresponse to excitation with a radiation presenting a higher or lowerfrequency (second frequency). In this manner, the first frequency of thebeam emerging from the optoelectronic device can be converted into asecond frequency that emerges then on a beam exit side of thewave-guiding stratified structure. Suitable materials for such aso-called up-conversion or down-conversion are common to those skilledin the art.

According to another embodiment of the present method or of theappertaining optical system, the beam exit side of the wave-guidingstratified system, which comprises at least one layer of a laser-activematerial, is coated with a layer reflecting the radiation of the secondfrequency so that the beam exit surface of the optoelectronic componentis used to form an optical resonator for the radiation of the secondfrequency. Whenever necessary for the function as resonator, the beamexit surface of the optoelectronic component may be coated with anadditional layer for reflection of the second frequency, prior to theapplication of the stratified system on the base. In this manner, awaveguide laser is formed y the save-guiding structure, which is pumpedby the optoelectronic component. To this end, the coating that ispossibly applied on the beam exit surface of the optoelectroniccomponent for reflection of the second frequency, must, of course, betransmitting for the first frequency. According to another embodiment,it is also possible to add further mirrors by structuring, polishingand/or subsequent coating with dielectric or metallic layers. One mirrormay be formed, for instance, by a structure in the form of a V-shapedretro reflector on the base.

Even though the above description refers essentially to anoptoelectronic component with a beam exit surface via which a beam isemitted, it is, of course, also possible in the present method and theappertaining system to use optoelectronic components, too, which emitseveral beams via several beam exit surfaces. The optoelectroniccomponent may be an isolated semiconductor diode laser with several beamexit surfaces, for example, or may be composed of several beam sourcesin succession. The application of an optoelectronic component includingseveral beam sources, particularly in the form of semiconductor diodelasers, offers advantages specifically when a waveguide laser is pumpedthat is formed by the wave-guiding stratified system. One essentialfeature of the present method is the application of an optoelectroniccomponent completely finished, i.e. fully operable, which may becommercially available, for instance, and is mounted on the base.

When an optoelectronic component is used that emits several beams viaseveral beam exit surfaces the wave-guiding stratified system is sodeposited and structured that all the emerging beams are guided in thedesired manner in this wave-guiding stratified system. In one expedientembodiment, the individual beams are converged through the wave-guidingstratified system on a reduced beam exit surface so that one beam with asmall cross-sectional area and a high intensity is available on the beamexit side of the wave-guiding stratified system. The wave-guidingstratified system is designed in the form of a beam coupler in thiscase.

A metal or dielectric substrate, in particular a cooling body, ispreferably used as base. With this configuration, improved cooling ofthe optical system is achieved at the same time. When the base isdesigned as cooling body it may present, for instance, cooling fins onthe underside or integrated cooling passages or any other means forcooling. The connection between the base and the optoelectroniccomponent may be achieved, for instance, via a soldered or adhesiveconnection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present method as well as the appertaining system will be brieflydescribed again in the following by embodiments, with reference to thedrawings, without a restriction of the general inventive idea. In thedrawing:

FIG. 1 shows different view of an optical system according to thepresent invention;

FIG. 2 illustrates individual exemplary steps of operation according tothe present method for the manufacture of an optical system according toFIG. 1; and

FIG. 3 shows one example of an optical system with a waveguide laseraccording to the present invention.

WAYS OF REALISING THE INVENTION

FIG. 1 shows different schematic views of an example of an opticalsystem according to the present invention. The partial view (a)illustrates a perspective view of such an optical system. In thispartial view, the beam-emitting optoelectronic component 1—which is asemiconductor diode laser with several beam exit surfaces for theemission of several beams in side-by-side relationship in the presentcase—can be clearly seen, which is mounted on the surface 5 of a base 4.A wave-guiding structure in the form of a wave-guiding stratified system6 is applied on the beam exit surface 3 of the optoelectronic component,in direct contact with the beam exit surfaces of the optoelectroniccomponent 1. The individual beams emerging from the optoelectroniccomponent 1 are guided here by the juxtaposed waveguides of thewave-guiding stratified system 6, which are formed in the presentexample.

In the partial view (b), this arrangement is illustrated again incross-section along the beam axes of the beams emerging from theoptoelectronic component 1. In this illustration, the connecting layer12 between the optoelectronic component 1 and the base 4 can be seen.The wave-guiding stratified system 6 consists of three superimposedlayers 7 to 9 whereof the middle layer 8 has a refractive index higherthan the refractive index of the neighbouring layers 7, 9. In thismanner, a waveguide is formed for the radiation emerging from theoptoelectronic component 1 via the beam exit surface 2 visible here. Themiddle layer 8 is in direct contact with the beam exit surface 2.

The partial view (c) shows again one part of this optical system in asectional view along the beam axis. In this illustration, the waveguideformed by the wave-guiding stratified system 6 for a single beam of theoptoelectronic component 1 can be clearly seen. By means of depositingthe individual layers 7 to 9 of this wave-guiding stratified system 6,the effect can be achieved that the middle layer region 8 is completelysurrounded by the neighbouring layers 7 and 9.

FIG. 2(a) is an exemplary illustration of one possibility to manufacturethe optical system shown in FIG. 1 in accordance with the presentmethod. In the first step (FIG. 2 a), a solder layer 12 is applied onone region on a base 4 and subsequently, the optoelectronic component 1is connected to the base 4 via this solder layer 12 so that a freesurface of the base 4 is located ahead of the beam exit surface 2 of theoptoelectronic component 1, seen along the beam direction.

Then, an optically wave-guiding stratified system 6 is located on thebase 4 ahead of the optoelectronic device 1 in such a manner that theradiation emerging from the beam exit surface 2 is guided within thelayers. The propagation of the radiation is restricted, in a mannerknown per se, to desired directions. Initially, a bottom layer 7 of thestratified system 6 is deposited via a mask 13 in direct contact withthe optoelectronic device 1 on the surface 5 of the base 4 FIG. 2 b).Once the bottom layer 7 has been deposited, a middle layer 8 isdeposited by means of a mask 13 in the same manner, which middle layercovers, in particular, the optoelectronic component 1 (FIG. 2 c).

In the present example, the middle layer 8 is subsequently structured bymeans of a laser beam 14 (FIG. 2 d) so as to create waveguides inside-by-side relationship, as is roughly indicated, too, in the partialview (a) of FIG. 1. Finally, the top layer 9 is deposited, in turn viathe mask 13, so that the arrangement of the wave-guiding structure 6 isachieved, which is illustrated in FIG. 1.

In this example, the individual layers 7 to 9 of the stratified system 6are deposited by an appropriate plasma depositing technique, e.g. laserdeposition, whilst the middle layer 9 is structure, for instance, bylaser ablation.

FIG. 3 illustrates eventually a further example of an optical systemaccording to the present invention, equally in two partial views (a) and(b) corresponding to the views (b) and (c) of FIG. 1. In this example,the middle layer 8 of the wave-guiding stratified system 6 consists of alaser-active material that can be pumped by the radiation of theoptoelectronic component 1 acting as pumping source. The partial view(a) moreover illustrates roughly two resonator mirrors in the form ofcoatings 11 on the beam exit side 10 of the wave-guiding stratifiedsystem 6 as well as on the beam exit side 3 of the optoelectronic device1. Due to these resonator mirrors, the wave-guiding stratified system 7represents a waveguide laser that is realised in direct contact with thepumping beam source, i.e. the optoelectronic component 1, on a commonbase 4. When the two resonator mirrors 11 are omitted it is possible toachieve a simple frequency conversion of the radiation of theoptoelectronic component 1 in this manner. The partial view (b)illustrates again the fundamental structure of the wave-guidingstratified system 6 for a beam, in a section taken in a directionorthogonal on the beam direction.

LIST OF REFERENCE NUMERALS

1 optoelectronic component 2 beam exit surface 3 beam exit side of theoptoelectronic component 4 base or carrier substrate 5 surface of thebase 6 wave-guiding stratified system 7 bottom layer 8 middle layer 9top layer 10 beam exit side of the wave-guiding stratified system 11(partially) reflecting coating (resonator mirror) 12 connecting layer 13mask 14 laser beam

1-25. (canceled)
 26. Method of manufacturing a beam-guiding and/orfrequency-converting optical system comprising providing a beam-emittingoptoelectronic component comprising at least one beam exit surface foremergence of a beam, and connecting the optoelectronic component to asurface of a base in such a manner that the beam emerging from the atleast one beam exit surface extends approximately in parallel with thesurface of said base, wherein after establishing connection of saidoptoelectronic component with said base, a wave-guiding stratifiedsystem composed of several layers is deposited and structured and/orlocally modified on the surface of said base for guidance and/orfrequency conversion of the beam, in such a manner that to create agap-free contact between said at least one beam exit surface and saidstratified system and achieve a pre-determinable beam guidance.
 27. Themethod according to claim 26, wherein at least one layer of saidwave-guiding stratified system is formed of a laser-active material thatis constructed and arranged to be excited by a first frequency of thebeam emerging from said optoelectronic component and emits a radiationof a higher or lower second frequency in response to excitation.
 28. Themethod according to claim 27, further comprising coating a beam exitside of said wave-guiding stratified system and, optionally, said beamexit surface of said optoelectronic component, with a layer at leastpartially reflecting the radiation of said second frequency to providean optical resonator for the radiation of said second frequency.
 29. Themethod according to claim 26, wherein at least three superimposed layersare deposited as the wave-guiding stratified system, whereof a middlelayer of said at least three superimposed layers has a refractive indexthat is higher than a refractive index of adjacent layers.
 30. Themethod according to claim 26 wherein said base is metallic or ceramic.31. The method according claim 26, wherein said base is a cooling body.32. The method according to claim 26, wherein said optoelectroniccomponent and said base are connected by soldering.
 33. The methodaccording to claim 26, further comprising structuring of the stratifiedsystem occurs while one or more of said layers of said stratified systemare deposited by application of one or more depositing masks.
 34. Themethod according to claim 26, wherein structuring of said stratifiedsystem is by local removal after one or more of said layers of saidstratified system are deposited.
 35. The method according to claim 26,wherein modification of said stratified system is by locally restrictedinfluence of energy for varying refractive index of a layer.
 36. Themethod according to claim 26, 33, 34 or 35, wherein low-temperatureprocesses are employed for depositing and structuring and/or localmodification of said stratified system.
 37. The method according toclaim 26, further comprising depositing and structuring one or morelayers on said base in direct contact with said wave-guiding stratifiedsystem to constitute further optical components.
 38. The methodaccording to claim 26, wherein a plurality of said at least one beamexit surface is used, with said wave-guiding stratified system beingstructured and/or locally modified for guidance and/or frequencyconversion of beams emerging from said plurality of beam exit surfaces.39. The method according to claim 38, wherein said wave-guidingstratified system is structured and/or locally modified so that thebeams emerging from said plurality of exit surfaces converge onto areduced beam exit surface.
 40. The method according to claim 26, whereinthe optoelectronic component includes one or more semiconductor diodelasers.
 41. A beam-guiding and/or frequency-converting optical systemcomprising a beam-emitting optoelectronic component comprising at leastone beam exit surface for emergence of a beam, connected to a surface ofa base in such a manner that the beam emerging extends approximately inparallel with the surface of said base, and a wave-guiding stratifiedsystem composed of a plurality of layers in gap-free contact with saidat least one beam exit surface deposited on the surface of said base forguidance and/or frequency conversion of the beam.
 42. The systemaccording to claim 41, wherein at least one layer of said wave-guidingstratified system comprises a laser-active material that is constructedand arranged to be excited by a first frequency of the beam emergingfrom said optoelectronic component for emission of radiation of a higheror lower second frequency in response to excitation.
 43. The systemaccording to claim 42, wherein a beam exit side of said wave-guidingstratified system and, optionally said at least one beam exit surface ofsaid optoelectronic component, are coated with a layer reflecting theradiation of said second frequency for forming an optical resonator forradiation of said second frequency.
 44. The system according to claim41, wherein said wave-guiding stratified system comprises at least threesuperimposed layers whereof a middle layer presents a refractive indexhigher than a refractive index of layers adjacent thereto.
 45. Thesystem according to claim 41, wherein said base is metal or ceramic. 46.The system according to claim 41, wherein said base is a cooling body.47. The system according to claim 41, further comprising one or morestructured layers deposited on said base in direct contact with saidwave-guiding stratified system to constitute further optical components.48. The system according to claim 41, wherein said optoelectroniccomponent includes a plurality of beam exit surfaces, with saidwave-guiding stratified system being structured and/or locally modifiedfor guidance and/or frequency conversion of the beams emerging from saidplurality of beam exit surfaces.
 49. The system according to claim 48,wherein said wave-guiding stratified system is structured and/or locallymodified so that the beams emerging from said plurality of beam exitsurfaces converge onto a reduced beam exit surface.
 50. The systemaccording to claim 41, wherein said optoelectronic component includesone or more semiconductor diode lasers.